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| author |   Shakeel Butt <shakeelb@google.com> | 2021-10-24 23:19:16 -0700 |
|---|---|---|
| committer |   Tejun Heo <tj@kernel.org> | 2021-10-25 07:26:00 -1000 |
| commit | 822bc9bac9e9a2f76a772a34f745962dfc223353 (patch) | |
| tree | c6899104e273f2537d1e3951d578a2b6069eb2ca /kernel/cgroup | |
| parent | cgroup: remove cgroup_mutex from cgroupstats_build (diff) | |
| download | linux-dev-822bc9bac9e9a2f76a772a34f745962dfc223353.tar.xz linux-dev-822bc9bac9e9a2f76a772a34f745962dfc223353.zip | |
cgroup: no need for cgroup_mutex for /proc/cgroups
On the real systems, the cgroups hierarchies are setup early and just
once by the node controller, so, other than number of cgroups, all
information in /proc/cgroups remain same for the system uptime. Let's
remove the cgroup_mutex usage on reading /proc/cgroups. There is a
chance of inconsistent number of cgroups for co-mounted cgroups while
printing the information from /proc/cgroups but that is not a big
issue. In addition /proc/cgroups is a v1 specific interface, so the
dependency on it should reduce over time.
The main motivation for removing the cgroup_mutex from /proc/cgroups is
to reduce the avenues of its contention. On our fleet, we have observed
buggy application hammering on /proc/cgroups and drastically slowing
down the node controller on the system which have many negative
consequences on other workloads running on the system.
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup')
| -rw-r--r-- | kernel/cgroup/cgroup-v1.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index fd14a60379c1..81c9e0685948 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -659,11 +659,9 @@ int proc_cgroupstats_show(struct seq_file *m, void *v) seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n"); /* - * ideally we don't want subsystems moving around while we do this. - * cgroup_mutex is also necessary to guarantee an atomic snapshot of - * subsys/hierarchy state. + * Grab the subsystems state racily. No need to add avenue to + * cgroup_mutex contention. */ - mutex_lock(&cgroup_mutex); for_each_subsys(ss, i) seq_printf(m, "%s\t%d\t%d\t%d\n", @@ -671,7 +669,6 @@ int proc_cgroupstats_show(struct seq_file *m, void *v) atomic_read(&ss->root->nr_cgrps), cgroup_ssid_enabled(i)); - mutex_unlock(&cgroup_mutex); return 0; } |